FIG. 6 is a diagram of an image display system used for displaying an intended image. This image display system includes an image signal generation apparatus 11, an image signal generator 12 contained in the image signal generation apparatus 11, and an image display apparatus 13.
In FIG. 6, the image signal generation apparatus 11 has an internal image signal generator 12, and outputs an image signal generated by this image signal generator 12. The image signal output from the image signal generation apparatus 11 is displayed at the image display apparatus 13.
FIG. 7 is a block diagram of the internal configuration of an image display apparatus 13 used in a conventional image display system such as that disclosed in Patent Document 1. The image display apparatus in FIG. 7 includes a signal input unit 21, a signal-for-display generator 22, a non-uniformity corrector 23, and a display unit 24.
Subsequently, an operation of the image display apparatus shown in FIG. 7 will be explained using FIGS. 6 and 7. As shown in FIG. 6, the image signal output from the image signal generation apparatus 11 is input to the image display apparatus 13. At this time, as shown in FIG. 7, the image signal is input to the signal input unit 21 of the image display apparatus.
The signal input unit 21 converts the image signal, which is received in a predetermined format, to a format that can be processed in the image display apparatus, and outputs it to the signal-for-display generator 22. As the signal input unit 21, it is conventional to use an analog-digital converter that converts an analog image signal to a digital signal, a digital signal processing circuit that converts a serial digital signal to a parallel digital signal, and the like.
The signal-for-display generator 22 receives the image signal output from the signal input unit 21, converts it to an image signal that can be displayed by the display unit 24, and outputs it. Specifically, it converts the resolution and frequency of the image signal such that they can be displayed using a display element.
With respect to the image signal generated by the signal-for-display generator 22, the non-uniformity corrector 23 sets a correction amount for each display position, and outputs a corrected signal. As a correcting means, there are a method of passing the image signal itself through a multiplier and changing the multiplication amount at each display position, and a method of using a lookup table to add/subtract a correction amount corresponding to a display position to/from the image signal.
The display unit 24 receives and displays an image signal output from the non-uniformity corrector 23.
While the non-uniformity corrector 23 is provided in a rear stage of the signal-for-display generator 22, similar effects can be achieved by providing it in a front stage of the signal-for-display generator 22. As another correction means, non-uniformity is corrected by controlling the light source at each position in a transmission-type display apparatus using liquid crystal or the like; since this method does not correct the image signal itself, it can be provided separate from the flow of the image signal.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 11-109885
However, conventional image display apparatuses have a drawback that the element used for display generates non-uniformity on the screen, whereby uniform display becomes impossible. Although there are several image display apparatuses that include means of correcting non-uniformity, the non-uniformity correction amount in each of these existing apparatuses is fixed. However, non-uniformity generated in a display element is greatly affected by the temperature and the like of the display element, and cannot be completely corrected with a fixed correction amount.